We just bought a new 18 x 52 Intex Ultra & are preparing the ground for set up right now. Before we fill I'll be ordering either a 2100 gph or 2650 gph Intex sand filter without copper, I'm hoping, and an intex SWG. I've been reading as much as I can here but would like advise from those that have an Intex SWG, Do I need to buy an expensive test kit or can I get away with a salt test strip & a smaller test kit?